The present invention concerns an integrated method of air separation and of energy generation and an integrated plant for the implementation of such a method.
In particular it relates to an integrated method of air separation for the production of oxygen-enriched fluid and possibly of nitrogen-enriched fluid.
It is well known to send a nitrogen-enriched gas from an air separation unit upstream of a combustion gas expansion turbine. The combustion chamber is fed with compressed air originating from an air compressor which can supply all or some of the air required by the air separation unit (ASU) as illustrated in EP-A-0538118. Alternatively as in the case of GB-A-2067668 all the air can originate from a dedicated compressor.
U.S. Pat. No. 5,664,411 shows a plant with three gas turbines and an air separation unit, the latter being fed solely by a dedicated compressor.
Generally for reasons of reliability, on one and the same site, there are two gas turbines and two air separation units which are substantially identical, producing both the impure oxygen required for the gasification of the fuels and nitrogen. Each separation unit can be fed from a gas turbine compressor and sends nitrogen solely to this same gas turbine which feeds it.
An aim of the invention is to alleviate the defects of the prior methods, in particular by allowing more flexible operation and more reliable startup. According to one object of the invention, there is provided an integrated method of air separation for the production of oxygen-enriched fluid and possibly nitrogen-enriched fluid in a plant comprising at least a first air separation unit comprising at least two distillation columns, a first air compressor, a first combustion chamber, a first expansion turbine, a second air compressor, a second combustion chamber and a second expansion turbine and a third air compressor, in which compressed air is sent from the first air compressor to the first combustion chamber and to the first air separation unit, compressed air is sent from the second air compressor to the second combustion chamber and to the first air separation unit, air is sent from the third air compressor to the first air separation unit, combustion gas is sent to the first expansion turbine from the first combustion chamber, combustion gas is sent to the second expansion turbine from the second combustion chamber and a nitrogen-enriched gas, possibly pressurized, is sent from the first air separation unit upstream of the first expansion turbine and/or upstream of the second expansion turbine.
It will be understood that the first air separation unit may be the only air separation unit of the facility or may be the first of several units.
The nitrogen-enriched gas is sent upstream of the first turbine: thus it may be sent to the combustion chamber, possibly after having being mixed with the fuel or another fluid, and/or it may be sent to the inlet of the turbine.
Preferably, an oxygen-enriched gas produced by the first air separation unit is sent to a gasification unit from which the fuel for the combustion chamber originates.
It may be useful to provide an xe2x80x9cair barxe2x80x9d which is a common pipe for air streams originating from various different compressors, be they air compressors also associated with a gas turbine, air compressors dedicated to one or more air separation units.
Preferably, all the air streams intended for an air separation unit arrive there through a common pipe.
It is even possible to provide a common compressed air pipe for several air separation units.
It is preferable to mix air streams originating from at least two different compressors, upstream of the main exchanger of the separation unit or better still upstream of adsorbent beds of the air separation unit.
According to other optional and alternative aspects of the invention:
at least 20% of the air stream treated by the first separation unit during nominal working originates from the third compressor, preferably at least 30% or 40% or 50% or 60% or 70%;
during reduced working as compared with nominal working, the first air separation unit receives at least 90% of its air or at least 80%, preferably at least 85% or 90% or 95% of its air from the third compressor or is fed exclusively by the third compressor (this reduced working may for example be during a transient phase of a change in working, during start-up or any other phase when working is reduced, that is to say the unit produces fewer products than the maximum quantity of products that it is presumed to produce);
during nominal working at most 70% of the air treated by the first air separation unit originates from the first and/or from the second compressor;
during nominal working at most 50% of the air treated by the first air separation unit originates from the first and/or the second compressors;
during nominal working at most 40% of the air treated by the first air separation unit originates from at least one of the first and second compressors;
compressed air is supplied to a second air separation unit, producing at least one oxygen-enriched fluid and possibly at least one nitrogen-enriched fluid, via at least one of the first and second compressors, and a nitrogen-enriched gas is sent from the second air separation unit upstream of one at least of the first and second expansion turbines;
the same compressor sends at least 80%, preferably at least 90% or even 100%, of the air which it compresses to the first and/or to the second air separation unit;
the third compressor does not feed any combustion chamber and/or feeds only the first air separation unit;
one dedicated compressor feeds the second air separation unit;
the air originating from at least the first compressor is expanded or compressed upstream of the first and/or of the second air separation unit;
the air originating from at least the second compressor () is expanded or compressed upstream of the first and/or of the second air separation unit;
an expansion turbine for air originating from one of the first, second or third air compressors is coupled to a compressor for air originating from another of the first, second and third air compressors;
air originating from the first compressor is mixed with air originating from the second compressor and/or air originating from the third compressor before being sent to the first air separation unit, and preferably before being purified in a single purification unit upstream of the air separation unit;
the nitrogen-enriched gas originating from the first air separation unit is expanded or compressed upstream of one at least of the first and second expansion turbines;
the nitrogen-enriched gas originating from the second air separation unit is expanded or compressed upstream of one at least of the first and second expansion turbines;
an expansion turbine for nitrogen-enriched gas originating from one of the air separation units is coupled with a compressor for nitrogen-enriched gas originating from the other air separation unit.